title: Evidence for Mg2, ATP-dependent accumulation of Ca2+ by the intracellular non-mitochondrial calcium store in uterine smooth muscle cells.
abstract: Using carbachol contracture as the experimental model for testing the properties of the intracellular calcium store in intact tissue and 45Ca2+ accumulation in the chemically skinned by digitonin smooth muscle cells isolated from oestrogen-dominated rat uterus the evidence for the presence of Mg2+, ATP-dependent Ca2+ pump in the non-mitochondrial store has been found which is supposed to play a key role in the process of refilling' of the store on the cytoplasmic level. The experiments performed on intact muscle showed that the functional activity of the carbachol-releasable Ca2+ store is critically dependent on Ca2+ entry. It is found that Ca2+ entry via voltage operated Ca2+ channels or on the Na(+)-Ca2+ exchange was needed to refill the store in this tissue. However, when Ca2+ extrusion systems located in the plasma membrane were inhibited by La3+, the store retained its ability to discharge and reaccumulate Ca2+ released on the regular basis suggesting the presence of the energy-dependent Ca2+ accumulating system in the store. The process of the store refilling was totally inhibited by cyclopiazonic acid. Chemically skinned uterine smooth muscle cells demonstrated the presence of Mg2+, ATP-dependent accumulation of Ca2+ in the non-mitochondrial (ruthenium red insensitive) intracellular store(s) potentiated by Ca(2+)-precipitating anions (potassium oxalate and phosphate), in a time- and concentration dependent way which was inhibited by Ca(2+)-ionophore A 23187 (5 microM) and cyclopiazonic acid with Ki = 0.4 microM. It is suggested that in the uterine smooth muscle of the oestrogen-dominated rats, nonmitochondrial receptor-operated intracellular calcium store is represented by endoplasmic reticulum.
authors.forename: L G
authors.initials: LG
authors.lastname: Babich
authors.lastname: Burdyga ThV
authors.forename: S G
authors.initials: SG
authors.lastname: Shlykov
authors.forename: S A
authors.initials: SA
authors.lastname: Kosterin
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors*; D002217:Carbachol; D002469:Cell Separation; D002478:Cells, Cultured; D003593:Cytoplasm / Q000378:metabolism; D004072:Digitonin / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D004967:Estrogens / Q000008:administration & dosage; D005260:Female; D007211:Indoles / Q000494:pharmacology; D007476:Ionophores / Q000494:pharmacology; D009130:Muscle, Smooth / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D019831:Sodium-Calcium Exchanger / Q000187:drug effects / Q000502:physiology; D014599:Uterus / Q000187:drug effects / Q000378:metabolism
chemical_list: D015220:Calcium Channels; D004967:Estrogens; D007211:Indoles; D007476:Ionophores; D019831:Sodium-Calcium Exchanger; D000001:Calcimycin; D000255:Adenosine Triphosphate; D002217:Carbachol; D000252:Calcium-Transporting ATPases; D004072:Digitonin; D002118:Calcium; C000543:cyclopiazonic acid